In this article, I’ll show you how to set up a simple but genius ZFS snapshot schedule that will automatically take snapshots of your data at regular intervals. This will help you protect your data and ensure that you always have a recent backup available.

Here’s how you can set up a ZFS snapshot schedule:

sudo nano /root/create_zfs_snapshot.sh

Add the following lines to the script:

#!/bin/bash

# crontab -e
# 0 * * * * /root/create_zfs_snapshot.sh

zfs destroy tankz@hourly-$(date +%H)
zfs snapshot tankz@hourly-$(date +%H)

zfs destroy tankz@daily-$(date +%A)
zfs snapshot tankz@daily-$(date +%A)

zfs destroy tankz@weekly-$(date +%U)
zfs snapshot tankz@weekly-$(date +%U)

zfs destroy tankz@monthly-$(date +%m)
zfs snapshot tankz@monthly-$(date +%m)

zfs destroy tankz@yearly-$(date +%Y)
zfs snapshot tankz@yearly-$(date +%Y)

Make the script executable:

sudo chmod +x /root/create_zfs_snapshot.sh

Add the script to the crontab to run every hour:

crontab -e

Add the following line to the crontab:

0 * * * * /root/create_zfs_snapshot.sh

This script will create snapshots of your ZFS dataset tankz every hour, day, week, month, and year. The snapshots will be named hourly-<hour>, daily-<day>, weekly-<week>, monthly-<month>, and yearly-<year>, respectively. This schedule will ensure that you always have a recent backup of your data available for recovery.

This is a great solution for cheap VPS with low memory. It can help you to run more services on a single VPS without running out of memory.

Here’s how you can set up ZRAM on your Linux system:

1. Install ZRAM:

sudo apt-get -uy install zram-config nohang

1. Enable and start the ZRAM service:

sudo service zram-config start

1. Check the status of the ZRAM service:

sudo service zram-config status

Sources:

• https://github.com/alexmyczko/autoexec.bat/blob/master/config.sys/ubuntu-system-zram
• https://docs.kernel.org/admin-guide/blockdev/zram.html
• https://unix.stackexchange.com/questions/594817/why-does-zram-occupy-much-more-memory-compared-to-its-compressed-value
• https://lore.kernel.org/lkml/20160606194836.3624-2-hannes@cmpxchg.org/
• https://unix.stackexchange.com/questions/32333/what-does-the-vm-swappiness-parameter-really-control

curl https://github.com/username.keys

You can try on my account:

curl https://github.com/ipepe.keys

This command will output the public SSH keys associated with the specified GitHub account. You can then copy the keys and add them to the authorized_keys file on the server or service where you need to use them.

Setup swap

sudo fallocate -l 1G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
sudo cp /etc/fstab /etc/fstab.bkp_before_swap_config
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
sudo sysctl vm.swappiness=10
sudo sh -c "echo 'vm.swappiness=10' >> /etc/sysctl.conf"

Setup docker and add current user to docker group

sudo apt install docker-compose docker.io
sudo usermod -aG docker $USER

Show IP address on tty login

sudo nano /etc/issue

Add the following lines to display the IP address of your network interface (replace enp2s0 with your actual interface name):

Ubuntu \n \l

enp2s0 (IPv4): \4{enp2s0}
enp2s0 (IPv6): \6{enp2s0}

First, identify your touchscreen device by opening the Terminal. You can do this by searching for “Terminal” in your applications menu, or by pressing Ctrl+Alt+T. In the terminal, type the following command:

xinput

This command will display a list of all input devices. Find your touchscreen in this list, which might be named something like “ELAN Touchscreen” or “FTSC1000:00 2808:1015”.

Next, disable the touchscreen using the xinput disable [id] command, replacing [id] with your touchscreen device’s ID number. If your touchscreen’s ID is 10, for instance, you would enter:

xinput disable 10

Please remember to replace [id] with your own device’s ID. Be careful not to disable other devices as it might affect the functionality of your mouse, keyboard, or other important input devices.

This method will only disable the touchscreen until the next reboot. For a permanent solution, consider adding the command to a startup script. However, the process to do this may vary depending on your desktop environment.

By following these steps, you can easily control the touchscreen feature on your Dell XPS 17 and make your Ubuntu 20.04 experience even more enjoyable.

Disclaimer: Be sure to replace “[id]” with the actual ID number of your touchscreen. Each hardware configuration will have a unique ID. Be careful not to disable any other devices, as you might lose the ability to use your mouse, keyboard, or other important input devices.

Before we start, remember that making changes to your system can have significant effects, especially when using the DiskPart utility or editing the Windows Registry. Always back up your data and double-check all steps.

Hiding a Volume Temporarily

Firstly, here’s how you can temporarily hide a volume using the DiskPart utility:

1. Open the Command Prompt as an Administrator (Press Win + X -> Choose “Command Prompt (Admin)”).
2. Launch DiskPart by typing diskpart and pressing Enter.
3. List all volumes by entering list volume.
4. Identify and select the volume you want to hide: select volume X (Replace X with the volume number).
5. Remove the drive letter to hide the volume: remove letter=Y (Replace Y with the letter assigned to the volume).

This will hide the chosen volume, and it won’t appear in File Explorer. However, the volume will reappear after a system restart.

Hiding a Volume Permanently

For a more permanent solution, you need to dive into the Windows Registry:

1. Press Win + R, type regedit and hit Enter to open Registry Editor.
2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices.
3. Find the registry key corresponding to the drive letter you want to hide: \DosDevices\X:, where X is the drive letter.
4. Right-click on the key, select Rename, and change \DosDevices\X: to \DosDevices\ZZX: (ZZ being a unique prefix).
5. Restart your computer.

Voila! The drive should remain hidden even after a system restart.

Note: Always exercise caution when modifying the Windows Registry as incorrect modifications can lead to serious system issues.

By following these steps, you can create a more streamlined and uncluttered workspace, ensuring that only the most essential volumes are in sight!

Instead of running each it block separately with the entire setup each time, a clever solution was provided by TestProf through their RuboCop cops. They encourage using one of RSpec’s excellent features – the aggregation of failures within a single example. This approach permits grouping independent assertions together, running all setup hooks only once and considerably boosting test suite performance by reducing the total number of examples.

This change required only a minor alteration to our .rubocop.yml file to enable the RuboCop cops:

# .rubocop.yml
require:
 - 'test_prof/rubocop'

One of the cops provided by TestProf is RSpec/AggregateExamples. Here’s an example of how to modify your tests to take advantage of it:

# before
it { is_expected.to be_success }
it { is_expected.to have_header("X-TOTAL-PAGES", 10) }
it { is_expected.to have_header("X-NEXT-PAGE", 2) }
its(:status) { is_expected.to eq(200) }

# after
it "returns the second page", :aggregate_failures do
  is_expected.to be_success
  is_expected.to have_header("X-TOTAL-PAGES", 10)
  is_expected.to have_header("X-NEXT-PAGE", 2)
  expect(subject.status).to eq(200)
end

Notice that we now have just a single it block with multiple assertions. This allows the setup (the before blocks) to run only once for this group of assertions, rather than once per assertion, dramatically speeding up our test suite.

Also, TestProf’s RuboCop cops come with an auto-correct feature, which can make these adjustments automatically!

For more details on this and other cops provided by TestProf, you can check out their documentation. Happy testing!

Sources:

• https://test-prof.evilmartians.io/#/misc/rubocop?id=rspecaggregateexamples

Built-in Method

Rails provides a built-in method to turn on query tracing. You can do this by setting the verbose_query_logs option to true in your config/application.rb file:

# config/application.rb
config.active_record.verbose_query_logs = true

This will log all SQL queries to your console.

Gem

Alternatively, you can use the active-record-query-trace gem to turn on query tracing. This gem provides more detailed information about the queries that are executed.

To use the gem, add it to your Gemfile:

# Gemfile
gem 'active-record-query-trace'

Then, enable query tracing in an initializer file:

# config/initializers/active_record_query_trace.rb
if Rails.env.development?
  ActiveRecordQueryTrace.enabled = true
end

This will log all SQL queries to your console, along with information about the source of the query (e.g. file name and line number).

Conclusion

By turning on ActiveRecord query tracing, you can get a better understanding of the SQL queries that are executed by your application. This can help you identify and fix performance issues, as well as debug any issues that arise.

URL: https://cad.onshape.com/documents/55ae3138e0cd7c325239208b/w/c97698491e3111712f79c19b/e/d2190ac9a7351530ae3efe66?renderMode=0&uiState=62f0911532b0144649ff3945